1. Field of the Invention
The present invention relates to a web processing system for slitting a wider web into a plurality of narrower webs for use as photographic photosensitive webs (films), and winding the narrower webs.
2. Description of the Related Art
Generally, web processing systems have a web slitting a device for slitting a wider web of film, paper, metal foil, or the like into a plurality of narrower webs, and a winding device for winding the narrower webs.
The web processing systems also have a side edge delivery device for delivering side edges that are severed off the wider web when it is slit. Heretofore, the side edge delivery device comprises delivery rollers and nip rollers for nipping and delivering the side edges. For details, reference should be made to Japanese laid-open patent publication No. 8-257990, for example.
When the wider web is slit into the narrower webs by rotary blades, it is necessary for the side edge delivery device to apply a predetermined level of tension to the side edges in order to give highly accurate transverse dimensions to the narrower webs.
If the side edges were not tensioned or were tensioned excessively, then the wider web that reaches the rotary blades would be flexed, resulting in a reduction in the accuracy of the transverse dimensions of the narrower webs.
One conventional side edge delivery device which is capable of applying tension to side edges (hereinafter referred to as xe2x80x9cconventional side edge delivery devicexe2x80x9d) is disclosed in Japanese laid-open patent publication No. 10-6126, for example.
The conventional side edge delivery device comprises nip rollers that are pressed against delivery rollers under a constant pressure by cylinders, and motors operatively coupled to the delivery rollers by respective clutches. The clutches are supplied with exciting currents that are variable to apply a desired tension to the side edges.
As described above, for imparting a desired tension to the side edges, the cylinders are connected to the respective nip rollers and the clutches are operatively coupled between the delivery rollers and the motors. However, the clutches are responsible for an increase in the manufacturing cost of the conventional side edge delivery device.
The motors are rotated at a constant speed at all times, and the exciting currents of the clutches are controlled to set the side edge tension to a desired value.
Therefore, while the slitting process is being suspended, the clutches slip at an increased speed, and hence tend to generate an increased amount of heat.
Winding devices that are in practical use for winding narrow webs having a small thickness ranging from 10 to 20 xcexcm, e.g., xc2xd-inch and 8 mm magnetic tapes, have a tension fluctuation ratio of xc2x15% or less.
However, winding devices for winding wide webs having a large thickness ranging from 100 to 150 xcexcm, e.g., photographic photosensitive webs (films), with a low tension fluctuation ratio, have not yet been developed in the art.
As shown in FIG. 15 of the accompanying drawings, a conventional film winding device 500 comprises a drive shaft 504 with an air tube 502 disposed therein, and a winding core 512 rotatably mounted on the drive shaft 504 by bearings 506, 508, for winding a film 510 therearound. The conventional film winding device 500 also includes a displacement transmitting member 516 disposed around the air tube 502 within the winding core 512 and having a felt pad 514 mounted on a radially outer surface thereof.
When compressed air is introduced into the air tube 502, the air tube 502 is expanded to displace the displacement transmitting member 516 radially outwardly for thereby pressing the felt pad 514 against an inner wall surface of the winding core 512 for slipping contact therewith.
The torque that is generated when the felt pad 512 slips against the winding core 512 is used as a tension applied to the film 510 when the film 510 is wound around the winding core 512.
However, the conventional film winding device 500 is disadvantageous in that the tension applied to the film 510 is not stable and the tension fluctuation ratio can only be lowered to about xc2x115% even if the conventional film winding device 500 is well conditioned. Furthermore, the conventional film winding device 500 is unable to produce large tension because of its principles of operation. The maximum tension that can be generated by the conventional film winding device 500 is about 10 N at the most, when the width of a narrow web to be wound is 35 mm, for example. If more tension is produced, then the film 510 that is wound tends to be deformed due to the heat. Moreover, since the air tube 502 is mounted in the drive shaft 504 and the felt pad 514 is attached to the radially outer surface of the displacement transmitting member 516, the conventional film winding device 500 is complex in structure and its maintenance needs to be carried out by skillful operators.
It is therefore an object of the present invention to provide a web processing system for winding relatively wide webs having a large thickness ranging from 100 to 150 xcexcm, e.g., photographic photosensitive webs (films), with a low tension fluctuation ratio of xc2x15% or less, while producing large tension easily and stably, the web processing system being constructed for easy maintenance.
Another object of the present invention is to provide a web processing system which can be manufactured inexpensively and is capable of slitting a wider web into a plurality of narrower webs having highly accurate transverse dimensions.
According to an aspect of the present invention, a winding device of a web processing system has a drive shaft having a flange, and a holder rotatably mounted on the drive shaft in covering relation to the flange, for winding the web therearound, the holder comprising a first torque adjustment unit rotatably mounted on the drive shaft and having a surface disposed in facing relation to a surface of the flange, the first torque adjustment unit supporting a plurality of magnets on the surface thereof, and a second torque adjustment unit rotatably mounted on the drive shaft and having a surface disposed in facing relation to an opposite surface of the flange, the second torque adjustment unit supporting a plurality of magnets on the surface thereof.
When the relative position of the first and second torque adjustment units is varied, the density of magnetic fluxes produced between the first and second torque adjustment units is varied.
When the drive shaft is rotated about its own axis, the flange positioned between the first and second torque adjustment units cuts the magnetic fluxes produced between the first and second torque adjustment units, generating eddy currents in the flange. Secondary magnetic fluxes produced in the flange by the eddy currents and the magnetic fluxes produced between the first and second torque adjustment units attract each other, producing a torque substantially proportional to a slipping speed, for example.
According to another aspect of the present invention, a winding device of a web processing system comprises a drive shaft having a ring, an annular conductor pressed against and secured to an outer circumferential surface of the ring, and a holder rotatably mounted on the drive shaft in covering relation to the ring, for winding the web therearound, the holder supporting on an inner circumferential surface thereof a magnet row of a plurality of magnets, the magnet row facing the annular conductor.
When the drive shaft is rotated about its own axis, the annular conductor cuts the magnetic fluxes produced between magnet rows, generating eddy currents in the annular conductor. Secondary magnetic fluxes produced in the flange by the eddy currents and the magnetic fluxes produced between the magnet rows attract each other, producing a torque substantially proportional to a slipping speed, for example.
According to still another aspect of the present invention, a winding device of a web processing system comprises a drive shaft having a torque transmitter, a support fixed to the torque transmitter, an annular conductor pressed against and secured to an outer circumferential surface of the support, and a holder rotatably mounted on the drive shaft in covering relation to the support, for winding the web therearound, the holder supporting on an inner circumferential surface thereof a magnet row of a plurality of magnets with a magnet holder, the magnet row facing the annular conductor.
When the drive shaft is rotated about its own axis, the annular conductor cuts the magnetic fluxes produced between magnet rows, generating eddy currents in the annular conductor. Secondary magnetic fluxes produced in the flange by the eddy currents and the magnetic fluxes produced between the magnet rows attract each other, producing a torque substantially proportional to a slipping speed, for example.
The number of magnets on the inner circumferential surface of the holder may be increased, and the magnets may be arranged in a plurality of magnet rows for changing the density of the magnetic fluxes generated between the magnet rows.
It is preferable that the magnets be spaced at a constant pitch on the holder.
Before the magnets are mounted in place, all the magnets may be measured for the strength of magnetic forces, and those magnets whose magnetic forces are weaker and those permanent magnets whose magnetic forces are stronger may be alternately arranged.
Since the torque can be generated on the holder without contacting the holder, even when a wide web having a large thickness ranging from 100 to 150 xcexcm, e.g., a photographic photosensitive web (film), is to be wound, a tension fluctuation ratio may be set to xc2x15% or less. Therefore, the winding device can produce large tensions easily and stably.
Since any contact members such as felt pads are not present, and no air tube is mounted in the drive shaft, it is not necessary to take into account the service life of wearable components, and hence the maintenance of the winding device is facilitated.
It is preferable to provide cooling means for cooling at least the drive shaft and the holder.
If a narrow web having a small thickness ranging from 10 to 20 xcexcm is to be wound, then since any tension required to be applied thereto may be small, the amount of heat generated in the winding process is small, and the web can be cooled by natural air cooling. However, if a wide web having a large thickness ranging from 100 to 150 xcexcm, e.g., a photographic photosensitive web (film), is to be wound, then since the amount of heat generated in the winding process is large, the wound web may tend to be deformed due to the heat.
The cooling means is capable of effectively dissipating the heat generated in the winding process. Therefore, the winding device is effective to prevent the wound web from being deformed due to the heat.
The drive shaft may have a hollow space defined therein, and the cooling means may have cooling air introducing means for introducing cooling air from outside of the holder into the holder and the hollow space in the drive shaft.
The cooling means may have cooling fins mounted on a surface of the holder.
The cooling air introducing means may comprise a first cooling air passage for guiding the cooling air into the holder, and a second cooling air passage disposed in a portion of the drive shaft covered by the holder for guiding the cooling air introduced into the holder into the hollow space in the drive shaft.
According to yet another aspect of the present invention, a web processing system has at least a web slitting device for slitting a wider web into a plurality of narrower webs, the web slitting device comprising a rotary blade assembly for slitting a wider web which is being fed, along the direction of feed into a plurality of narrower webs, and side edge delivery means for delivering side edges produced from the wider web when the wider web is slit into the narrower webs, the side edge delivery means comprising a side edge delivery roller rotatable in a direction to deliver the side edges, a nip roller rotatable with the side edge delivery roller while gripping the side edges between the side edge delivery roller and the nip roller, and a nip roller pressing mechanism for pressing the nip roller against the side edge delivery roller under a predetermined pressure, the side edge delivery roller being rotatable at a peripheral speed higher than a peripheral speed of the rotary blade assembly.
The nip roller pressing mechanism may comprises a cylinder for displacing the nip roller in a direction toward the side edge delivery roller or a direction away from the side edge delivery roller, and a regulator for regulating an air pressure supplied to the cylinder to control the pressure under which the nip roller is pressed against the side edge delivery roller.
The peripheral speed of the side edge delivery roller may be higher than the peripheral speed of the rotary blade assembly by a value ranging from 0.5% to 5%.
The pressure applied from the nip roller to the side edge delivery roller is adjusted to apply a predetermined tension to the side edges. Consequently, the narrower webs are prevented from suffering an error in their transverse dimensions as when the tension applied to the side edges is released or the tension applied to the side edges becomes greater than the tension applied to the narrower webs. Therefore, if the narrower webs are used as movie films or photographic negative films, then they assure high image quality.
The web processing system may further comprise a motor and a pair of speed reducer mechanisms, the rotary blade assembly and the side edge delivery roller being operatively coupled to the motor via the speed reducer mechanisms, respectively. This arrangement allows the web slitting device to be manufactured relatively inexpensively.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.